extern(C) register passing bug

foo.cpp

#include <stdio.h>

struct Foo
{
        double a;
        void *p;
};

extern "C" Foo foo2(Foo foo, double a, double b, double c)
{
        printf("a=%f, b=%f, c=%f\n\n",a,b,c);
        Foo fo {1.0,0L};
        return fo;
}

extern "C" Foo foo()
{
        Foo fo {1.0,0L};
        return fo;
}

foo.d

import std.stdio;

struct Foo
{
	double a;
	void *p;
}

extern(C) Foo foo();
extern(C) Foo foo2(Foo foo, double a,double b, double c);

void main(string[] args)
{
	auto f = foo();
	writeln(f);
	auto f2 = foo2(f,1.0,2.0,3.0);
	writeln(f2);
}